Issue No. 65 July 2009 s DISTANT EKO di r The Kuiper Belt Electronic Newsletter Edited by: Joel Wm. Parker [email protected] www.boulder.swri.edu/ekonews CONTENTS News & Announcements ................................. 2 Abstracts of 16 Accepted Papers ........................ 3 Abstracts of 1 Thesis ................................. 13 Newsletter Information .............................. 14 1 NEWS & ANNOUNCEMENTS There were no new TNO/Centaur/SDO discoveries announced since the previous issue of Distant EKOs. Deleted/Re-identified objects: 2003 UW292 = 2005 UN524 Current number of TNOs: 1093 (including Pluto) Current number of Centaurs/SDOs: 243 Current number of Neptune Trojans: 6 Out of a total of 1342 objects: 548 have measurements from only one opposition 538 of those have had no measurements for more than a year 288 of those have arcs shorter than 10 days (for more details, see: http://www.boulder.swri.edu/ekonews/objects/recov_stats.jpg) 2 PAPERS ACCEPTED TO JOURNALS Herschel Open Time Key Programme: TNOs are Cool: A Survey of the Transneptunian Region Thomas G. M¨uller1, Emmanuel Lellouch2, Hermann B¨ohnhardt3, John Stansberry4, Antonella Barucci2, Jacques Crovisier2, Audrey Delsanti2, Alain Doressoundiram2, Elisabetta Dotto5, Ren´eDuffard6, Sonia Fornasier2, Olivier Groussin7, Pedro J. Guti´errez6, Olivier Hainaut8, Alan W. Harris9, Paul Hartogh3, Daniel Hestroffer10, Jonathan Horner11, Dave Jewitt12, Mark Kidger13, Csaba Kiss14, Pedro Lacerda15, Luisa Lara6, Tanya Lim16, Michael Mueller4, Raphael Moreno2, Jose-Luis Ortiz6, Silvia Protopapa3, Miriam Rengel3, Pablo Santos-Sanz6, Bruce Swinyard16, Nicolas Thomas17, Audrey Thirouin6, and David Trilling18 1MPE Garching, Germany; 2Observatoire de Paris-Meudon, France; 3MPS Katlenburg-Lindau, Germany; 4University of Arizona, USA; 5Osservatorio Astronomico di Roma, Italy; 6IAA-CSIC Granada, Spain; 7Laboratoire d’Astrophysique de Marseille, France; 8ESO, Chile; 9DLR Berlin, Germany; 10Observatoire de Paris, France; 11Open University, Milton Keynes, UK; 12UCLA, USA; 13ESAC, Villafranca del Castillo, Spain; 14Konkoly Observatory, Hungary; 15Queen’s University Belfast, Ireland; 16RAL Didcot, UK; 17University of Bern, Switzerland; 18University Northern Arizona, USA Over one thousand objects have so far been discovered orbiting beyond Neptune. These trans- Neptunian objects (TNOs) represent the primitive remnants of the planetesimal disk from which the planets formed and are perhaps analogous to the unseen dust parent-bodies in debris disks observed around other main-sequence stars. The dynamical and physical properties of these bodies provide unique and important constraints on formation and evolution models of the Solar System. While the dynamical architecture in this region (also known as the Kuiper Belt) is becoming relatively clear, the physical properties of the objects are still largely unexplored. In particular, fundamental parameters such as size, albedo, density and thermal properties are difficult to measure. Measurements of thermal emission, which peaks at far-IR wavelengths, offer the best means available to determine the physical properties. While Spitzer has provided some results, notably revealing a large albedo diversity in this population, the increased sensitivity of Herschel and its superior wavelength coverage should permit profound advances in the field. Within our accepted project we propose to perform radiometric measurements of 139 objects, including 25 known multiple systems. When combined with measurements of the dust population beyond Neptune (e.g. from the New Horizons mission to Pluto), our results will provide a benchmark for understanding the Solar debris disk, and extra-solar ones as well. To appear in: Earth, Moon and Planets, Issue 105 (2009 August) For preprints, contact [email protected] ................................................... ............................................... 3 The History of the Solar System’s Debris Disc: Observable Properties of the Kuiper Belt Mark Booth1, Mark C. Wyatt1, Alessandro Morbidelli2, Amaya Moro-Mart´ın3,4, and Harold F. Levison5 1Institute of Astronomy, Madingley Rd, Cambridge CB3 0HA, UK 2Observatoire de la Cˆote d’Azur, Nice, France 3Centro de Astrobiologia - CSIC/INTA, 28850 Torrej´on de Ardoz, Madrid, Spain 4Department of Astrophysical Sciences, Peyton Hall, Ivy Lane, Princeton University, Princeton, NJ 08544, USA 5Department of Space Studies, Southwest Research Institute, Boulder, CO 80302, USA The Nice model of Gomes et al. suggests that the migration of the giant planets caused a plan- etesimal clearing event which led to the Late Heavy Bombardment (LHB) at 880 Myr. Here we investigate the IR emission from the Kuiper belt during the history of the Solar System as described by the Nice model. We describe a method for easily converting the results of N-body planetesimal simulations into observational properties (assuming black-body grains and a single size distribu- tion) and further modify this method to improve its realism (using realistic grain properties and a three-phase size distribution). We compare our results with observed debris discs and evaluate the plausibility of detecting an LHB-like process in extrasolar systems. Recent surveys have shown that 4% of stars exhibit 24 µm excess and 16% exhibit 70 µm excess. We show that the Solar System would have been amongst the brightest of these systems before the LHB at both 24 and 70 µm. We find a significant increase in 24 µm emission during the LHB, which rapidly drops off and becomes undetectable within 30 Myr, whereas the 70 µm emission remains detectable until 360 Myr after the LHB. Comparison with the statistics of debris disc evolution shows that such depletion events must be rare occurring around less than 12% of Sun-like stars and with this level of incidence we would expect approximately one of the 413 Sun-like, field stars so far detected to have a 24 µm excess to be currently going through an LHB. We also find that collisional processes are important in the Solar System before the LHB and that parameters for weak Kuiper belt objects are inconsistent with the Nice model interpretation of the LHB. To appear in: Monthly Notices of the Royal Astronomical Society For preprints, contact [email protected] or on the web at http://uk.arxiv.org/abs/0906.3755 ................................................... ............................................... Trans-Neptunian Region Architecture: Evidence for a Planet Beyond Pluto Patryk Sofia Lykawka1 and Tadashi Mukai2 1 Kinki University, International Center for Human Sciences (Planetary Sciences), 3-4-1 Kowakae, Higashiosaka, Osaka, 577-8502, Japan 2 Kobe University, Department of Earth and Planetary Sciences, 1-1 rokkodai-cho, nada-ku, Kobe, 657-8501, Japan Trans-Neptunian objects (TNOs) orbiting in the Edgeworth-Kuiper Belt carry precious infor- mation about the origin and evolution of the Solar System. The Kuiper Belt has a very complex orbital structure. Indeed, TNOs exhibit surprisingly large eccentricities, e, and inclinations, i, and are classified in distinct dynamical classes. Here we propose that the Kuiper Belt orbital structure can be explained by a massive scattered planetesimal with tenths of the Earth’s mass, which later remained in the system in a distant stable orbit (an outer planet). Near the end of planet formation, 4 the outer planet was firstly scattered by one of the icy giant planets, then it dynamically excited the primordial planetesimal disk over at least tens of Myr, reproducing the levels observed at 40–50 AU and the truncation of the disk at about 48 AU before planet migration. Later, the outer planet was captured by a distant resonance with Neptune of the type r:1 or r:2 (e.g., 6:1, 7:1, ...), acquiring an inclined stable orbit (=100 AU; 20–40◦), thus preserving the Kuiper Belt over ∼4 Gyr. Our model explains the following: 1) Depletion of the inner Kuiper Belt; 2) The entire currently known resonant populations in the Kuiper Belt, including Neptune Trojans and resonant TNOs in distant resonances (> 50 AU); 3) Formation of scattered and detached TNOs, including analogues of (136199) Eris, 2004 XR190, (148209) 2000 CR105, and (90377) Sedna; 4) Classical TNOs and their dual nature of cold and hot populations; 5) Orbital excitation of classical TNOs; 6) The Kuiper Belt outer edge at about 48 AU; 7) Loss of ∼99% of the initial total mass of the Kuiper Belt through dynamical depletion and enhanced collisional grinding; 8) Neptune’s current orbit at 30.1 AU. In summary, our scenario consistently reproduces all main aspects of Kuiper Belt architecture with unprecedented detail. The best constraints obtained from the model for the outer planet are: aP = 100 − 175 AU ◦ ◦ (currently near or inside an r:1 or r:2 resonance), qP > 80 AU, iP = 20 − 40 , and apparent mag- nitude mP ∼ 15 − 17 mag at perihelion (assuming an albedo of 0.1–0.3 and qP = 80 − 90 AU). Published in: Advances in Geosciences, Volume 15 (Planetary Science), 293 For preprints, contact [email protected] or on the web at http://sites.google.com/site/patryksofialykawka/ ................................................... ............................................... Kozai Cycles, Tidal Friction, and the Dynamical Evolution of Binary Minor Planets Hagai B. Perets1 and Smadar Naoz2 1 Weizmann Institute of Science, P.O. Box 26, Rehovot 76100, Israel 2 Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel In recent years, many binary minor planets